The harlequin ladybird (Harmonia axyridis) was introduced in numerous countries around the world as a biological control agent but nowadays it is considered as a pest itself. It is a highly invasive species that has negative impacts on native biodiversity, may affect some crops, and causes a nuisance to humans. Despite its relevance worldwide, the invasion by H. axyridis in South America has received little attention. Here we used a citizen science approach to study the distribution of H. axyridis in Argentina where the species was intentionally introduced in 1986. We also informally tested and evaluated the preferences for different methods for reporting records: iNaturalist website, Google form, email, WhatsApp, and Facebook. Most records were reported through WhatsApp and iNaturalist. We found that H. axyridis is widely distributed in Argentina but there are large gaps, particularly in arid regions. The invasion seems to be recent in the south of the country. Citizen science is a valuable tool for mapping invasive alien species in a large country like Argentina, and will help to monitor the continuous expansion of H. axyridis. Keywords Alien species Á Biological invasion Á Coccinellidae Á iNaturalist Á Pampa Á Patagonia Electronic supplementary material The online version of this article (

Volcanic eruptions often modify the structure and function of ecosystems at large geographical scales. However, the extent to which species diversity patterns respond to these major natural disturbances is still poorly known. We tested the shape of the species richness – elevation relationship (SRER) and its environmental correlates (thermal environment at ground level, vegetation structure and soil attributes) before and 6 months after (in the first summer) the most recent eruption of the Puyehue Cordon Caulle volcanic complex (PCCVC), which caused an extensive ash accumulation in northwestern Patagonia, Argentina. We re‐established 32, 100‐m2 sampling plots of nine pitfall traps, placed every 100 m of altitude from the base to the summit of three mountains differentially affected by ash deposition, and from which we had pre‐eruption data on richness and environmental variables. Coverage‐based rarefaction/extrapolation curves showed a local post‐eruptive decrease in richness on only one mountain. Generalised additive models (GAMs) showed no significant differences between pre‐ and post‐eruptive SRER shapes. Partial least squares structural equation modelling (PLS‐SEM) showed that woody vegetation and the thermal environment accounted for most of the variation in richness before and after the eruption. Soil attributes were only indirectly associated with beetle richness and the association was mediated by woody vegetation. Ash accumulation ameliorated the thermal environment, promoting a local increase in beetle richness. The rapid recovery of the SRER shape and its environmental correlates suggest that the structuring of local diversity patterns at temperate latitudes of the southern hemisphere is resilient to major volcanic eruptions.

RESUMEN.Dado el rol fundamental de los artrópodos y los insectos en el funcionamiento de los ecosistemas áridos, para manejar estos ambientes resulta necesario conocer su relación con las características de la vegetación local. Dentro de la región fitogeográfica del Chaco, en Los Llanos de la provincia de La Rioja, Argentina, existen grandes cambios en la vegetación en distancias cortas, lo que determina un gradiente de heterogeneidad vegetal. El objetivo de este estudio fue analizar la respuesta de los artrópodos epígeos a estos cambios. En este gradiente se seleccionaron 3 ambientes (Salinas, Interfaz y Monte) en los que se recolectaron artrópodos y, dentro de éstos, insectos mediante trampas de caída durante 7 días en la temporada cálida. Se determinó la abundancia total de artrópodos e insectos y la riqueza de especies/morfoespecies de insectos. Se evaluó la asociación entre los ambientes y la abundancia y riqueza de especies mediante un ANOVA de medidas repetidas. Para evaluar la completitud del muestreo se utilizaron estimadores de riqueza no-paramétricos (Chao 1 , Jackniffe 1 y Bootstrap) y curvas de acumulación de especies. Para evaluar la estructura de la comunidad se usaron curvas de rango-abundancia y análisis multivariados. Se recolectaron en total 8380 artrópodos, de los cuales 5902 fueron insectos que se agruparon en 14 órdenes, 31 superfamilias, 35 familias y 114 especies/morfoespecies. El ambiente con mayor heterogeneidad vegetal (Monte) presentó la mayor abundancia de artrópodos y la mayor abundancia y riqueza de insectos. Las familias de insectos más abundantes y de mayor riqueza fueron Formicidae (Hymenoptera) y Tenebrionidae (Coleoptera). Chao 1 y Bootstrap fueron los mejores estimadores de riqueza. En este estudio se encontró que la abundancia, la riqueza y la composición de especies de artrópodos, y particularmente insectos, estuvo asociada a un gradiente de vegetación.[Palabras clave: variabilidad, entomofauna epígea, indicadores, suelo, región chaqueña, La Rioja] ABSTRACT. Of arthropods and plants: Arthropod fauna diversity in a vegetation gradient in Los Llanos of La Rioja province (Argentina).Given the fundamental role of arthropods and insects in the functioning of arid ecosystems, it is of key importance to understand their relationships with the environment, particularly for the development of future conservation efforts. Within the phytogeographic region of Chaco, in Los Llanos (La Rioja province, Argentina), great changes in vegetation occur within short distances, determining a pronounced gradient of plant heterogeneity. The aim of this study was to analyse the response of epigaeic arthropods to these changes. In this gradient, three environments were selected (Salinas, Interface and Monte), in which we collected arthropods and insects using fall traps during seven days during the warm season. Total abundance of arthropods and insects, and richness of insect species/morpho-species were determined. The association between the environments and the abundance and richness of species wa...